Flight control actuators are used in aircraft to move control surfaces (rudder, elevators and ailerons). Currently, it is mainly linear actuators which are used with elevators and ailerons, because of the very low backlash inherent in linear actuators.
However, if a linear actuator is used, the tailplane or wing carrying the elevator or aileron must be capable of accommodating the linear actuator at full extension, which requires a considerable amount of space inside the tailplane or wing to be set aside for the linear actuator.
Rotary control actuators, although more compact than linear actuators, tend to have greater backlash, which can lead to flutter if the actuators are used to move flight control surfaces.